1. Field of the Invention
The invention concerns radio-diagnostic equipment including an X-ray tube and a shutter for defining an aperture of modifiable size through which the X-ray radiation can pass. The shutter consists of a plurality of lamellae which lie adjacent to each other at the sides of the aperture and are independently positionable in a longitudinal direction depending on the size of the object to be examined. An X-ray image intensifier is coupled to a television camera for generating video signals which are applied to a monitor for reproduction of the video signals. An evaluation circuit also responsive to the video signals applies control signals to a position regulating device for controlling the position of the individual lamellae.
2. Description of the Prior Art
U.S. Pat. No. 3,631,249 describes a primary radiation shutter for radio-diagnostic equipment in which a semi-transparent shutter consisting of two shutter plates attenuates the lateral radiation in a beam of X-rays which otherwise, especially in the case of extremities, fall full strength onto the X-ray image intensifier input for the fluorescent screen and thus produce light areas which impair the recognition of details in the actual area under examination. The use of semi-transparent shutter plates attenuates these irradiated lateral areas so that visibility in the areas under observation is increased and furthermore, contrasting objects, for example, surgical instruments which are advanced from the sides of the area under examination, are still clearly visible. To adjust the position of the object under examination with respect to the radio-diagnostic equipment, the shutter plates are placed on a rotatable shutter disk. To adjust the width of the unimpaired path of the X-rays, both shutter plates can be moved toward each other until, for example, all irradiated areas have disappeared. In the case of curvilinear contours, as is normally the case, no adjustment to contours can be obtained with these rectilinear frontal edges of the shutter plates. Either a large part of the object to be examined is also attenuated in the process or large parts of the television image are still irradiated and the recognition of details continues to be reduced.
Furthermore, from DE-OS No. 29 05 202 an illuminated light viewing box is shown for viewing transparent rectangular pictures. The area on which the picture is placed can be darkened by adjustment of a plurality of parallel narrow width cover strips. By placing the pictures on the edge of the light viewing box their size is automatically perceived. Initially the strips prevent illumination of the picture. Thereafter, only those strips which cover the picture are moved, via a motor, until the film is illuminated up to its lower edge. Several films can only be simultaneously illuminated if their vertical dimensions are identical. This, however, means also that an alignment to irregular contours by the lamellae of this light viewing box is not possible.
One object of the invention is to create radio-diagnostic equipment of the kind mentioned above in which the semi-transparent shutter adjusts as precisely as possible to the contours of the object under examination so that none or only small areas of the examined object are covered or only small areas in the vicinity of the object are not covered.